CN114401819B - Sharpener with manual honing table - Google Patents

Abstract

The present invention relates to an apparatus and method for sharpening cutting tools (190). The sharpener (100) has a base unit (102) and one or more manual sharpening modules (104, 106). The base unit has a housing (108) surrounding at least one flexible grinding disc (118, 120, 118A, 118B, 118C) rotated by a motor (124). Each flexible grinding disc is adjacent a powered sharpening station (130, 132) to perform a primary sharpening operation on the tool. Each manual sharpening module can be removably attached to the base unit. The manual sharpening station (146) incorporates at least one sharpening element (148, 200A, 200B, 202A, 202B, 206A, 206B, 208) to perform a secondary sharpening operation on the tool. Each manual sharpening module also has external guide surfaces (134, 136) forming part of the corresponding powered sharpening station. When two powered sharpening stations are used, the manual sharpening module can be individually placed between the powered sharpening stations to provide opposing outer guide surfaces for each powered sharpening station.

Description

Sharpening device with manual honing table

Background

Cutting tools are used in a variety of applications to cut or otherwise remove material from a workpiece. A variety of cutting tools are well known in the art including, but not limited to, knives, scissors, shears, blades, chisels, blades, saws, drills, and the like.

Cutting tools often have one or more transversely extending straight or curved cutting edges along which pressure is applied to cut. The cutting edge is often defined along the intersection of opposing surfaces (inclined surfaces) that intersect along a line along the cutting edge.

In some cutting tools (such as many types of conventional kitchen knives), the opposing surfaces are generally symmetrical; other cutting tools, such as many types of scissors and chisels, have a first opposing surface extending in a generally normal direction and a second opposing surface that is inclined relative to the first surface.

Complex blade geometries may be used, such as multiple sets of inclined surfaces at different respective angles that taper to the cutting edge. Scalloping or other discontinuous features may also be provided along the cutting edge, such as in the case of a serrated knife.

The cutting tool becomes dull over time after prolonged use, and thus sharpening operations are required to be performed on the dulled cutting tool to restore the cutting edge to a higher sharpness. A variety of sharpening techniques are known in the art, including the use of grinding wheels, grindstones, abrasive cloths, abrasive belts, and the like.

Disclosure of Invention

Various embodiments of the present disclosure are generally directed to an apparatus and method for sharpening a cutting tool, such as, but not limited to, a kitchen knife.

In some embodiments, a sharpener for sharpening a cutting tool having a cutting edge is provided. The sharpener has a housing, a flexible sharpening disk mounted within the housing to a central shaft to provide a powered sharpening stage, a motor disposed within the housing and configured to rotate the flexible sharpening disk in a selected rotational direction, and a manual sharpening module removably attached to the housing at a location adjacent the powered sharpening stage. The manual sharpening module has a power table guide surface configured to support a first side of the cutting tool during presentation of an opposite second side of the cutting tool against the flexible abrasive disk to effect a primary sharpening operation of the cutting edge. The manual sharpening module also has an elongated access slot for movement of the cutting tool along the cutting tool traction axis against the manual sharpening element to effect a secondary sharpening operation on the cutting edge.

In a related embodiment, a sharpener for sharpening a cutting tool having a blade with opposite first and second sides converging to an intervening cutting edge is provided. The sharpener includes a housing, first and second flexible sharpening disks mounted in spaced relation within the housing to a central shaft to provide opposing first and second power sharpening stages, a motor disposed within the housing and configured to rotate the first and second flexible sharpening disks in a selected direction of rotation, and a manual sharpening module affixed to the housing between the first and second power sharpening stages. The manual sharpening module has opposed first and second guide surfaces configured to support the opposed first and second sides of the blade, respectively, during presentation of the respective second and first sides of the blade against the respective first and second flexible abrasive disks. The manual sharpening module also has a honing station having an elongated access slot for presentation of the cutting edge against a manual honing element disposed within the access slot.

In a further related embodiment, a method is provided for sharpening a cutting tool having opposed first and second sides converging to an intervening cutting edge. The method includes inserting a cutting tool into a first power blade sharpening stage of a power sharpener to perform a primary sharpening operation on the cutting edge, the power sharpener having a housing enclosing a motor configured to rotate a first flexible abrasive disk in a selected rotational direction, and a removably attached manual sharpening module having a body with a power stage guide surface and an internal manual sharpening element, the power stage guide surface supporting a second side of the cutting tool during contact engagement against the first flexible abrasive disk; and pulling the cutting tool through the elongated slot of the manual sharpening module to pull the cutting tool against the manual sharpening element to perform a secondary sharpening operation on the cutting edge.

These and other features and advantages of the various embodiments may be understood by review of the following detailed description in conjunction with the drawings.

Drawings

Fig. 1 provides an isometric representation of a power tool sharpener constructed and operative in accordance with various embodiments of the present disclosure.

Figures 2A and 2B provide respective front and side views of the sharpener of figure 1.

Figure 3 shows a top plan view of the sharpener to illustrate the engagement of the manual sharpening module of the sharpener with the base unit of the sharpener in some embodiments.

Fig. 4A depicts a primary sharpening operation using a rotatable flexible disk of a base unit.

Fig. 4B shows the relationship between the disk holder and the flexible disk during the primary sharpening operation of fig. 4A.

Figure 5A is a top plan view of a secondary sharpening operation using a manual sharpening module.

Figure 5B shows a side view of a secondary sharpening operation.

Figure 6 illustrates the sharpening geometry achieved on the blade using the primary and secondary sharpening operations of figures 4-5 in some embodiments.

Fig. 7A and 7B depict different presentation angles provided by respective manual sharpening modules.

Fig. 8A and 8B show an internal view of the base unit.

Fig. 9A-9D illustrate alternative configurations for a manual sharpening module in further embodiments.

Fig. 10A and 10B illustrate different alternative configurations for a flexible abrasive disk in some embodiments.

Fig. 11 shows an alternative configuration for a rotatable flexible abrasive disk in a further embodiment.

Detailed Description

Various embodiments of the present disclosure are generally directed to a powered knife and tool sharpener, and a method for using the sharpener. As explained below, the sharpener includes a base unit with a powered sharpening medium and one or more manual sharpening modules with a manually activated sharpening medium. Within the base unit, an internal motor drives a central transverse shaft to which one or more flexible rotatable abrasive discs are mounted. It is envisaged that two discs will be used, one on each side of the shaft, but this is not required. The motor shaft is parallel to the disc shaft and power transmission is performed using a power transmission mechanism such as a belt and pulley system.

A fixed sharpening guide is provided to enable a user to repeatedly present opposite sides of a cutter or other cutting tool against an inwardly facing rotating surface of the abrasive disk. The flexible disk may incorporate sandpaper or similar flexible media adapted to provide an abrasive surface that removes material from the presented cutting tool to conform the exterior shape of the cutting tool to a desired cutting geometry.

In at least some embodiments, the disk may be rotated at two different speeds, a slower "sharpening" setting and a faster "shaping" setting. Each may be activated by pressing a corresponding button located near the rear of the sharpener housing, which in turn causes the motor to operate at a different setting to achieve the desired sharpening operation.

A manual sharpening module is removably attached to the central top of the base unit. When two disks are used, the manual sharpening module may be positioned between opposing rotatable abrasive disks. The manual sharpening module has a central slot through which a user may insert the blade after a powered sharpening operation using the abrasive disk. The manual sharpening module may be used when the module is attached to the base unit, or may be used in a hand-held manner when the user holds the module in his hand or places the module on a suitable support surface, such as a table. The purpose of the manual sharpening module is to perform a fine (honing) sharpening operation on the cutting edge of the tool after the tool has been sharpened using the powered abrasive.

The module incorporates a manual sharpening element which may take the form of a double bevel edge grinding wheel having two frustoconical surfaces facing each other. The edge grinding wheel may be formed from a single piece of ceramic and inclined at an acute angle relative to the central slot. The advancing and retracting of the blade provides a honing action to the blade because the blade is simultaneously acted upon by the two frustoconical discs. Honing removes burrs and provides fine shaping of the cutting edge. Other arrangements of manual sharpening elements may be used including, but not limited to, a pair of intersecting sharpening elements such as grinding wheels, bars, plates, blocks, and the like.

In further embodiments, two different manual sharpening modules are provided for use with the base unit of the sharpener. One manual sharpening module is configured for use with a knife having a relatively thin blade (such as a kitchen knife), while the other sharpening module is configured for use with a knife having a relatively thick blade (such as a small folding knife). Different manual sharpening modules may be adapted to provide different sharpening geometries, such as different shapes or angles, to the cutting tool. As mentioned above, the module may be used either when attached to the housing, when held in the hand of a user, or by placing the module on a flat base surface.

The outer surface of each module provides an angled support (guide) surface for use during sharpening against the abrasive disk in the base unit. Different manual sharpening modules may provide different angles of presentation of the respective blades against the rotating media. In some embodiments, the small folding knife module has a greater sharpening angle (e.g., about 25 degrees) than the kitchen knife module (e.g., about 20 degrees). In this manner, the selected sharpening module may provide not only the desired rough sharpening angle when the tool is subjected to a powered rough sharpening operation, but also a suitable corresponding fine honing operation to provide the desired fine sharpening angle when the tool is subsequently honed.

The two modules may be removed and attached to the housing by sliding the associated module forward and engaging a rigid hook that locks the associated module in place. Removal of the module allows the top cover of the base unit to be raised using a set of hinges, thereby providing easy access to the abrasive disk and other internal aspects of the sharpener. Instead, mounting the module to a rigid hook locks the top cover in place. In some cases, a fixed scissor support is formed in the top surface of the base unit to allow a user to sharpen a pair of scissors against a selected one of the abrasive discs when the module is removed from the base unit.

The abrasive disk may be mounted to the central shaft using an annular disk holder. The disc holder covers a substantial portion of the backing layer of each abrasive disc, such as by having a radius nominally about 50% of the radius of the associated abrasive disc. This places the edge of the disk holder in a position below the contact area on the opposite side of the associated disk to provide a biasing force to increase surface pressure and material take-off (MTO) rate during sharpening operations. In some cases, the function of the holder is to provide a higher surface pressure for thicker blades and a lower surface pressure for thinner blades.

The powered flexible abrasive disk may take a variety of configurations. In some embodiments, the abrasive disk is formed of double-sided sandpaper so as to have opposing outer abrasive surfaces on the intermediate backing layer. Other configurations may be used, such as a flexible abrasive disk with a foam middle layer that compresses to allow for conformal formation during sharpening operations.

These and other features and advantages of the various embodiments can be appreciated from a review of fig. 1, which shows a power tool sharpener 100. The power tool sharpener 100 includes a base unit 102 and a pair of releasably engaged manual sharpening modules 104, 106. The module 104 is shown connected to the base unit 102 and the module 106 is shown separate from the base unit. Any one of the modules may be mounted to the base unit as desired. In some cases, the base unit is also referred to herein as a main unit or power unit.

As explained in more detail below, the module 104 is generally configured for relatively thin blades (e.g., "kitchen knife modules") and the module 106 is generally configured for relatively thick blades (e.g., "small folding knife modules"). It should be appreciated that the provision of two (or more) modules is merely exemplary and not required. Furthermore, in at least some embodiments, the removable nature of the module is not required.

As further depicted in fig. 2A and 2B, the base unit 102 has a housing 108 formed from a base member 110 and a top cover 112. The base member 110 includes a set of support members (feet) 114 having anti-slip features adapted to support the sharpener 100 on an underlying base surface 116. Although not shown separately, the respective manual sharpening modules 104, 106 may be provided with similar anti-slip features for individual support on the base surface and use.

A pair of rotatable flexible abrasive discs 118, 120 are enclosed within the housing 108. The flexible abrasive discs 118, 120 (sometimes also referred to as first and second discs) are arranged to rotate about a central axis 122, the central axis 122 being rotated using a drive system having a motor 124, a belt 126 and a pulley 128, as generally depicted in fig. 2B. Additional details regarding the drive system are provided below.

A pair of sharpening ports 130, 132 (also sometimes referred to as powered sharpening stages) are provided in the top cover 112 to provide access to the inner surfaces of the flexible abrasive disks 118, 120. Opposing guide surfaces 134, 136 are provided on each sharpening module 104, 106. In this manner, during a powered sharpening operation, a user may place opposite sides of the blade of the cutter against the respective guide surfaces 134, 136 in sequence to sharpen the cutting edge of the cutter against the respective flexible abrasive disk 118, 120. For this reason, the guide surface may also be referred to as a powertable guide surface or an external guide surface. It should be noted that in this configuration, both flexible abrasive discs 118, 120 rotate in the same direction (e.g., downward and transverse, etc.) in each sharpening stage relative to the cutting tool.

Fig. 3 provides a top plan representation of the sharpener 100 to illustrate the mounting of a selected manual sharpening module (in this case, the small folding knife module 106) onto the base unit 102. By sliding the module 106 forward, a mechanical engagement is formed with the alignment feature 138 of the top cover 112 and the rigid retention hook 140 extending from the base member 110 through the opening 142. In this way, engagement of either module locks the top cover to the base unit (e.g., locks the housing closed). For reference, the support 144 in fig. 3 may be used to support a pair of scissors during sharpening operations against the flexible abrasive disk 118.

Each of the modules 104, 106 includes a central aperture (slot) 146 extending in a longitudinal direction along the overall length of the associated module. The slot 146 (also sometimes referred to as a manual sharpening or honing station) provides non-contact access to an internal manual sharpening member, depicted in fig. 3 as a double bevel edge grinding wheel having two frustoconical surfaces 150, 152 facing each other. The sharpening wheel 148 is free to rotate about a sharpening hub 154, which sharpening hub 154 is inclined at an acute angle, such as about 25 degrees, relative to the slot 146.

Although not limiting, it is contemplated that the edge grinding wheel will be formed of ceramic, although other materials may also be used. The intersection of the respective axes of the double bevel edge grinding wheel 148 along the frustoconical surfaces 150, 152 provides honing of the opposite sides of the blade. The slot allows the blade of the tool to advance and retract against the grinding wheel along the length of the cutting edge.

Referring again to the base unit 102 in fig. 3, the clearance surfaces 156, 158 protrude toward the contact guide surfaces 134, 136 of the associated sharpening module to allow access to the respective flexible disk. The clearance surfaces 156, 158 are best seen in fig. 2A (not shown in fig. 3), and when the modules 104, 106 are installed, respectively, the clearance surfaces 156, 158 form the exterior of the sharpening pockets 130, 132 during sharpening.

Fig. 4A and 4B illustrate additional aspects of the respective flexible abrasive disk 118, 120 in some embodiments. It should be appreciated that these figures are schematic in nature and thus serve to generally illustrate sharpening operations performed against the flexible abrasive disk 118, 120. The central shaft 122 from fig. 2 is more fully shown as including a central shaft 160 supported by respective bearing assemblies 162, 164. The shaft 160 has threaded ends 166, 168 that are threadably engaged by a pair of annular disc retainers 170, 172.

The disk holders 170, 172 are nominally identical and each has a central annular groove 176. The groove 176 receives the belt 126 (see fig. 2) on the side with the flexible abrasive disk 118. The retainer is configured to be easily installed and removed by a user threadably engaging the retainer with the threaded end of the shaft. This allows the user to replace or rotate (flip) the rotatable flexible abrasive disk 118, 120. The retainer may take any suitable configuration including metal, plastic, etc.

As depicted in fig. 4B, the retainers 170, 172 cover a majority of the back side of each flexible abrasive disk 118, 120, providing mechanical support for the inner radial extension of the associated disk. Adjacent the holder is a contact region 178, generally depicted in fig. 4B, which is the region against which the cutting edge of the blade 180 (shown in fig. 4A) contacts the associated disk during rotation of the disk. The contact area 178 is positioned along the proximal side of the flexible abrasive disk 118, 120 closest to the user such that the cutting edge is sharpened on a single side of the central shaft 122; it can be noted from fig. 3 that the inwardly directed guide surfaces 134, 136 render the front portion of the cutting edge non-contact with the other side of the disc, generally as depicted by the so-called "non-contact" region 178A.

Because each holder is offset from the contact area, the flexible disk can deflect back and follow the contour of the blade. As shown, the edges of the retention tray are concave such that a generally thicker blade applies a higher surface pressure and a thinner blade applies a lower surface pressure. A central hole (hole) 179 in the disk allows the disk to slide over the associated threaded ends 166, 168 of the central shaft 160 during disk installation.

Returning to fig. 4A, the blade 180 has opposite sides 182, 184. The side 182 is contactingly supported against the guide surface 134 of the manual sharpening module 106 to sharpen the first side of the blade against the flexible abrasive disk 118. Side 184 is similarly contactingly supported against guide surface 136 to sharpen an opposite second side of the blade against flexible abrasive disk 120. Because the guide surfaces 134, 136 are angled inwardly (see top plan view of fig. 3), the blade 180 in fig. 4A follows this angle and is therefore angled with respect to the end view vantage point of fig. 4A.

The primary (or powered) sharpening operation can be performed by placing each side of the blade 180 into a respective sharpening port 130, 132 in turn. In some cases, the motor 124 may be configured to rotate the respective flexible abrasive disk 118, 120 at a fixed rotational rate suitable for primary sharpening operations. In other cases, the motor 124 may be configured to operate at different speeds and/or for different periods of time to achieve different forms of sharpening.

In one non-limiting embodiment, the primary sharpening operation using the flexible abrasive disk 118, 120 may include a sharpening cycle that includes a first higher (sharpening) speed for rapidly grinding the bevel and a second lower (thinning) speed for reducing/removing any burrs formed in the first higher speed. The time of each speed is controlled by a motor control circuit (not shown) coupled to the motor. The user simply presses a button on the device to perform this sequence.

After the sharpening cycle, a second forming cycle may be initiated by an alternate input from the user. The forming cycle provides a third higher (forming) speed/time to reshape/repair the dull or damaged edge, followed by a low (finish) speed to remove/reduce any burrs formed during previous high speed operations. This third higher forming speed increases the centrifugal force component acting on the disc and subsequently further increases the material take-off (MTO) of the forming step.

The reduction in speed provided during the finish grinding speed of the sharpening and forming cycle reduces the centrifugal force component acting on the disc and subsequently further reduces the MTO of the finish grinding step.

Fig. 5A and 5B illustrate the edged grinding wheel 148 within each module 104, 106 in more detail in connection with a cutting tool (cutter) 190, wherein the blade 180 forms a portion of the cutting tool (cutter) 190. The edge grinding wheel 148 may have a single piece or multiple piece construction and may have any suitable outer surface configuration to provide honing and finishing of the blade 180. As will be appreciated, as the blade advances and the edge grinding wheel rolls about the shaft 154, the respective tapered surfaces 150, 152 apply compressive forces to opposite sides of the blade. The shaft 154 is tilted at a desired bevel angle to rotate about the bevel axle 155.

During manual (secondary) sharpening operations, including after the powered (primary) sharpening operation against the flexible abrasive disk 118, 120 as described above is completed, the user may place the blade 180 into the slot 146 (honing station) and advance/retract the blade a suitable number of times, such as ten times (10X), against the sharpening wheel 148 along the cutting tool traction axis 186, as depicted by the reciprocating arrow 186A. The user can grasp the handle 188 attached to the blade 180 of the knife 190 to manipulate the blade during primary sharpening operations and secondary sharpening operations in the respective powered and manual sharpening stages (e.g., sharpening ports 130, 132 or slot 146). The honing operation refines the cutting edge 191 established at the intersection of the respective sides 182, 184 of the insert.

Referring again to fig. 4A, it will be noted that during primary sharpening operations and secondary sharpening operations, the user guides the blade 180 in the same general direction (e.g., away from the user), but during primary sharpening operations the blade is deflected inwardly by the tapered guide surfaces 134, 136, and during secondary sharpening operations in a front-to-back direction along the traction axis 186. This amount of deflection may vary, but may be on the order of about 10 degrees to about 30 degrees. Other ranges of bevel angles may be used as desired.

Fig. 6 shows a schematic cross-sectional view of a blade 180 handled by the sharpener 100 in some embodiments. Typically, blade 180 is provided with a raised sharpening geometry such that side 182 has one or more linear ranges 182A and one or more curvilinear ranges 182B, and side 184 similarly has linear and curvilinear ranges 184A and 184B. The different sharpening speeds and media may provide micro-bevels and other features to enhance the sharpness and durability of the cutting edge 191. One such micro-ramp is indicated at 191A. The micro-chamfer 191A locally increases the angle of the blade near the cutting edge to strengthen the blade and improve the sharpness and durability of the cutting edge. Blade 180 is shown nominally symmetrical about centerline 192, but other blade geometries, including asymmetrical geometries, may be sharpened in a similar manner. It should be noted that the centerline 192 in fig. 6 is nominally perpendicular to the traction axis 186 in fig. 5A.

Fig. 7A and 7B illustrate the differences between the various manual sharpening modules 104, 106 in some embodiments. The kitchen knife module 104 in fig. 7A accommodates a thinner blade 180A and provides a first angle of presentation, such as nominally about 20 degrees. The pocket knife module 106 in fig. 7B accommodates a thicker blade 180B and provides a second, different presentation angle, such as nominally about 25 degrees. Other angles may be used as desired.

In some cases, further microcracking may be provided by taking a given blade and first supporting the blade at a first angle (e.g., 20 degrees) against the power disc using the module 104, and then supporting the blade at a second angle (e.g., 25 degrees) against the power disc using the second module 106. Although not limiting, the respective slots 146 in the modules 104, 106 may have different respective widths to accommodate the associated blades such that the slots in the module 106 may be slightly wider than the slots in the module 104. It should be noted that the slot 146 does not act as a guide surface during the secondary manual sharpening operation.

Fig. 8A and 8B illustrate respective isometric views of the base unit 102 of the sharpener 100 in some embodiments. In these figures, the modules 104, 106 have been separated from the base unit, and the top cover 112 has been raised relative to the base member 110 using a pair of hinges at the rear of the unit (one such hinge being indicated at 194).

The various internal elements described above are depicted in fig. 8A and 8B, including flexible abrasive disks 118, 120; a motor 124; a belt 126; a pulley 128; a holding hook 140; disc holders 170, 172; and motor control board/circuitry (not separately numbered). As shown, these elements are supported by a central boss 196 extending upwardly from the base member 110.

A pair of disc magnets 198 are disposed in the base member 110 below the respective flexible abrasive discs 118, 120. The magnet collects, via magnetic attraction, the cuttings (particles, etc.) that have been removed from the blade when the disc was used for the primary sharpening operation.

Note that the aforementioned pulley 128 is attached to a motor shaft 199 driven by the motor 124. The motor shaft 199 is nominally parallel to the central shaft 160 supporting the flexible abrasive disk 118, 120. The central shaft is received within the central boss 196, but is depicted as being included in fig. 4A. Thus, the belt 126 acts as a power transmission belt to transmit power from the motor to the central shaft and thus to the flexible abrasive discs 118, 120 and disc holders 170, 172.

Fig. 9A-9D illustrate alternative configurations for the respective manual sharpening modules 104, 106 described above. Fig. 9A shows an alternative manual sharpening module 104A in which a pair of intersecting elements 200A, 200B are provided. The elements 200A, 200B are characterized as intersecting cylindrical ceramic rods.

After sharpening the blade on the flexible abrasive disk, as described above, the user can place the blade 180 (fig. 5A-5B) into the slot 146 in a position to bisect the honing elements 200A, 200B and draw the blade along the full length of the blade along the draw axis 186 (fig. 5A). This action serves to refine the cutting edge 191 by grinding action or cold forming the fine streaks present on the cutting edge after sharpening. It should be noted that the respective angles of the bars 200A, 200B may be selected relative to the angles of the guide surfaces 134, 136 to achieve a desired microcut of the cutting edge of the tool.

Fig. 9B shows an alternative manual sharpening module 104B in which a pair of intersecting disks 202A, 202B are arranged as shown. The disks 202A, 202B are hard metal disks rotatable about shaft members 204A, 204B, the shaft members 204A, 204B extending along an axis of rotation nominally parallel to the traction axis 186, wherein a tool is withdrawn along the traction axis 186 through the slot 146. In this way, the discs 202A, 202B provide a hollow abrasive (concave) sharpening geometry for the retracted cutting tool.

Fig. 9C shows yet another alternative manual sharpening module 104C in which sharpening elements 206A, 206B are provided. Elements 206A, 206B are each characterized as rigid metal plates that intersect as shown. The plates may be formed of any suitable rigid material, such as carbide or the like, and form v-shaped grooves through which the tool may be pulled along a pulling axis 186 within the slot 146 to honing the cutting edge of the tool. As previously described, the angle of the inwardly facing cutting surfaces (represented at 206C and 206D) may be different than the angle of the guide surfaces 134, 136 and may be selected relative to the angle of the guide surfaces 134, 136.

Fig. 9D provides another alternative manual sharpening module 104D in which only a single sharpening element 208 is provided. Sharpening element 208 has a grinding surface 208A that is angled within slot 146 to provide a secondary sharpening operation on one side of blade 180. Sharpening element 208 may take the form of a sharpening block or some other configuration. Fig. 9D shows that although it is contemplated that the secondary sharpening operation may involve a pair of intersecting sharpening elements, this is not required as a single sharpening element or more than two sharpening elements may be used. Similarly, while the foregoing embodiments have shown the use of two powered sharpening elements (e.g., flexible abrasive disks 118, 120), other forms and numbers of powered sharpening elements may be used, including just one powered sharpening element, or more than two powered sharpening elements.

Fig. 10A and 10B illustrate additional configurations that may be used for the powered flexible abrasive disk 118, 120 in some embodiments. Fig. 10A shows a single-sided flexible abrasive disk 118A having a single abrasive layer 210 attached to a backing layer 212. In this case, the abrasive layer is arranged to face inwardly and the associated disc holders 170, 172 are clamped to the backing layer 212.

Fig. 10B shows a double-sided flexible abrasive disk 118B in which the aforementioned layers 210, 212 and a second abrasive layer 214 are located on opposite sides of the backing (middle) layer. An advantage of the configuration in fig. 10B is that once a selected one of the abrasive layers 210, 214 has been sufficiently worn, a user can easily lift the top cover 112, remove the associated disk holder, reverse the orientation of the double-sided flexible abrasive disk 118B and reinstall the disk holder as in fig. 8A-8B.

Another configuration may provide a powered sharpening port to enable the cutting tool to alternately be presented against each side of the double-sided abrasive disk to sharpen each side of the tool in turn. In the latter case, multiple powered sharpening guide surfaces may be incorporated into the manual sharpening module, and the manual sharpening element within the manual sharpening module may be offset from the powered sharpening stage, rather than necessarily located therebetween.

The abrasive layer can take any number of suitable forms and abrasive (particle size) levels. In some cases, these layers are formed from a sandpaper medium having a grit size in the range of about 120 to 240. Other ranges and forms of abrasive particles may be used as desired. The backing layer is any suitable flexible material, such as cloth or paper. It is contemplated that the abrasive layers on the individual disks will have a common level of abrasion, but this is not required as one surface may have a coarser particle size and the other surface may have a finer particle size.

Fig. 11 illustrates yet another alternative configuration for the flexible abrasive disk 118C, which may be used in some embodiments for the respective flexible abrasive disk 118, 120. The flexible abrasive disk 118C includes opposing abrasive layers 216, 218 bonded to opposite sides of an intermediate compressed elastomeric substrate 220. The substrate 220 may take a variety of forms, such as foam rubber. This allows the abrasive layers 216, 218 to deform as described above while the substrate 220 provides a backing force against the surface pressure provided by the presentation of the blade 180.

While it is contemplated that the various embodiments discussed herein have used a powered abrasive media in the form of a flexible abrasive disk, aspects of the various embodiments may be used with other forms of removable media, such as, but not limited to, annular abrasive belts, rigid grinding wheels, and the like.

It is to be understood that even though numerous characteristics and advantages of the various embodiments of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the disclosure, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims (24)

1. A sharpener for sharpening a cutting tool having a cutting edge, the sharpener comprising:

a housing;

a flexible abrasive disk mounted to a central shaft within the housing to provide a powered sharpening stage;

a motor disposed within the housing and configured to rotate the flexible abrasive disk in a selected rotational direction; and

a manual sharpening module removably attached to the housing at a location adjacent the powered sharpening stage, the manual sharpening module having a power stage guide surface configured to support a first side of the cutting tool during presentation of the opposite second side of the cutting tool against the flexible abrasive disk to effect primary sharpening operation on the cutting edge, the manual sharpening module further having an elongated access slot for movement of the cutting tool along a cutting tool traction axis against a manual sharpening element to effect secondary sharpening operation on the cutting edge.

2. The sharpener of claim 1 wherein said flexible sharpening disk is a first flexible sharpening disk, said power stage being a first power stage sharpening stage, and said power stage guide surface being a first power stage guide surface, wherein said sharpener further comprises a second flexible sharpening disk mounted to said central shaft within said housing to provide a second power stage sharpening stage, wherein said manual sharpening module further has a second power stage guide surface configured to support said second side of said cutting tool during presentation thereof against said second flexible sharpening disk, and wherein said manual sharpening module is disposed between said first and second power stage sharpening stages.

3. The sharpener of claim 1 wherein said power table guide surface is skewed at an intermediate angle of 10 degrees to 30 degrees relative to said cutting tool traction axis.

4. The sharpener of claim 1 wherein said motor has a motor shaft with a pulley attached, a power transmission belt extending from said pulley to said central shaft to transmit power from said motor to said central shaft, and said central shaft and said motor shaft being nominally parallel.

5. The sharpener of claim 1 wherein said powered sharpening stage is formed by attaching said manual sharpening module to a top surface of said housing such that said powered stage guide surface forms one side of said powered sharpening stage and a portion of said housing forms an opposite second side of said powered sharpening stage.

6. The sharpener of claim 1 wherein said housing includes a base member and a cap connected to said base member using a hinge assembly, wherein a rigid hook extends from said base member through an opening in said cap to engage said manual sharpening module and lock said cap to said base member, and wherein removal of said manual sharpening module from said hook enables said cap to pivot relative to said base member via said hinge assembly to provide user access to said first and second flexible abrasive disks.

7. The sharpener of claim 1 wherein said manual sharpening element of said manual sharpening module comprises a sharpening wheel.

8. The sharpener of claim 7, said sharpening wheel including a pair of facing frustoconical surfaces and being mounted at a selected acute angle relative to said slot such that when said cutting tool is retracted along said cutting tool traction axis, said cutting edge presents and rolls along said wheel providing a compressive force on opposite sides of said cutting tool.

9. The sharpener of claim 1 wherein said manual sharpening element of said manual sharpening module comprises at least a selected one of a sharpening block, a sharpening bar, a sharpening disk, or a metal plate.

10. A sharpener for sharpening a cutting tool having a blade with opposite first and second sides converging to an intervening cutting edge, the sharpener comprising:

a housing;

first and second flexible abrasive discs mounted to a central shaft in spaced apart relation within the housing to provide opposed first and second power blade sharpening stages, wherein the abrasive surfaces of the respective first and second flexible abrasive discs move in a common direction relative to the cutting tool;

a motor disposed within the housing and configured to rotate the first and second flexible abrasive disks in a selected rotational direction; and

a manual sharpening module affixed to the housing between the first and second powered sharpening stages, the manual sharpening module having opposed first and second guide surfaces configured to support the opposed first and second sides of the blade, respectively, during presentation of the corresponding second and first sides of the blade against the respective first and second flexible sharpening disks, the manual sharpening module comprising a honing stage having an elongated access slot to facilitate presentation of the cutting edge against a manual honing element disposed within the access slot.

11. The sharpener of claim 10 wherein said manual honing element of said manual sharpening module includes a pair of intersecting elements forming a v-shaped channel, said cutting tool being configured to be pulled through said v-shaped channel during a honing operation.

12. The sharpener of claim 10 wherein said manual honing element of said manual sharpening module comprises at least a selected one of a frustoconical bevel wheel, a pair of steel plates, a pair of abrasive sticks, a pair of rotatable disks, or a single abrasive piece.

13. The sharpener of claim 10 further comprising first and second annular disc retainers configured to threadably engage opposing first and second ends of said central shaft to secure said first and second rotatable flexible abrasive discs thereto, each of said first and second annular disc retainers extending a portion of the total radius of said associated first or second rotatable flexible abrasive disc to provide a biasing force to an opposing second side of said associated first or second rotatable flexible abrasive disc during presentation of said cutting edge of said cutting tool against a contact region on a first side of said associated first or second rotatable flexible abrasive disc.

14. The sharpener of claim 10 wherein each of said first and second flexible abrasive discs is characterized as a single sided abrasive disc having an abrasive layer on a first side and a non-abrasive backing layer on an opposite second side.

15. The sharpener of claim 10 wherein each of said first and second flexible abrasive discs is characterized as a double sided abrasive disc having first and second abrasive layers on opposite sides of an intermediate backing layer.

16. The sharpener of claim 15 wherein said intermediate backing layer is formed of a selected one of cloth, paper or foam rubber.

17. The sharpener of claim 10 further comprising a magnet disposed within said housing adjacent a selected one of said first or second rotatable flexible abrasive discs to magnetically retain the cuttings in response to a primary sharpening operation.

18. The sharpener of claim 10 wherein said manual sharpening module is configured to be removably attached to said housing via sliding engagement of a first retaining member on a body portion of said manual sharpening module with a second retaining member of said housing.

19. The sharpener of claim 10 wherein said manual sharpening module is characterized as a first manual sharpening module and said opposing first and second guide surfaces of said first manual sharpening module extend at a first selected guide angle, wherein said sharpener further comprises a second manual sharpening module having a second manual honing element in a second honing station and opposing third and fourth guide surfaces extending at a different second selected guide angle, wherein each of said first and second manual sharpening modules is independently mounted between said first and second power sharpening stations to provide a different sharpening angle to said cutting tool against said respective first and second flexible abrasive discs.

20. A method for sharpening a cutting tool having opposed first and second sides converging to an intervening cutting edge, the method comprising:

inserting the cutting tool into a first power sharpening stage of a power sharpener to perform a primary sharpening operation on the cutting edge, the power sharpener having a housing enclosing a motor configured to rotate a first flexible abrasive disk in a selected rotational direction, and a removably attached manual sharpening module having a body with a power stage guide surface and an internal manual sharpening element, the power stage guide surface supporting the second side of the cutting tool during contact engagement against the first flexible abrasive disk; and

the cutting tool is pulled through an elongated slot of the manual sharpening module to pull the cutting tool against the manual sharpening element to perform a secondary sharpening operation on the cutting edge.

21. The method of claim 20, further comprising removing the manual sharpening module from the housing of the powered sharpener after the inserting step and before the pulling step.

22. The method of claim 20 wherein the sharpener further comprises a second flexible abrasive disk mounted to the central shaft within the housing to provide a second powered sharpening stage, and wherein the method further comprises subsequently inserting the cutting tool into the second powered sharpening stage to perform a second primary sharpening operation on the cutting edge, the manual sharpening module having a second powered stage guide surface that supports the first side of the cutting tool during contact engagement against the second flexible abrasive disk.

23. The method of claim 22, wherein the manual sharpening module is characterized as a first detachable manual sharpening module that is detachably attachable to the housing, wherein the first and second power stage guide surfaces of the first detachable manual sharpening module extend at a first selected angle, and wherein the method further comprises removing the first detachable manual sharpening module from the housing and mounting a second detachable manual sharpening module to the housing between the first and second power stage, the second detachable manual sharpening module having a second manual sharpening element in a second elongated slot and opposing third and fourth power stage guide surfaces that extend at different second selected angles to form respective portions of the first and second power stage.

24. The method of claim 20, further comprising magnetically retaining cuttings generated during the primary sharpening operation using a magnet disposed within the housing adjacent the first flexible abrasive disk.